The invention relates to a hydrodynamic coupling having a pump impeller and a turbine impeller which together form a toroidal operating chamber. The operating chamber is used to receive an operating medium, for example oil or water, which transmits a torque.
The invention relates to a hydrodynamic coupling having a pump impeller and a turbine impeller which together form a toroidal operating chamber. The operating chamber is used to receive an operating medium, for example oil or water, which transmits a torque.
There are hydrodynamic couplings which are continuously filled with operating mediumxe2x80x94also referred to as constant couplings. However, there are also hydrodynamic couplings in which the operating chamber can be filled and emptied in a controllable mannerxe2x80x94also referred to as flow-controlled and filling-controlled, hydrodynamic couplings. The invention is concerned with the last-mentioned type of coupling. A coupling of this type has been disclosed in DE 197 06 652 A1.
Hydrodynamic couplings are used to transmit a torque from a driving motor to a machine, for example from an electric motor to a grinding machine or to a conveying system. On account of the operating characteristics of a coupling of this type, the torque is transmitted from the motor to the machine in a very elastic manner. In particular when starting up, i.e. when the motor is rotating and the machine is at a standstill, the curve of the torque transmitted to the machine only rises slowly. If the driving motor is an electric motor then the latter is brought up to its nominal speed under no-load conditions.
Flow-controlled, hydrodynamic couplings are of particularly significantly used in the mining industry. Here they are connected, for example, between an electric motor and a conveyor belt. In this connection, an important application area is what are referred to as scraper chain conveyors. In this case too the coupling ensures a gentle transmission of torque, specifically not only in the starting-up phase, but also when the scraper conveyor is running, namely if the scraper conveyor comes up against particularly hard material during its operation.
In the meantime, the motors have been developed further. The tilting moment of the motors has been increased. However, the couplings of the previous type of construction cannot produce this increased tilting moment, so that torque is not transmitted to a sufficient extent from the motor to the machine.
The invention is based on the object of designing a driving device having a motor and a flow-controlled, hydrodynamic coupling in such a manner that during the starting-up operation sufficient torque is transmitted from the motor to the machine even if the load exerted by the machine is very high.
This object is achieved by a flow-controlled, hydrodynamic coupling having an operating chamber which is formed from a pump impeller and a turbine impeller and is intended for introducing an operating medium. In order to make it possible for the operating chamber to be completely filled at a slip of 100% even in the case of large torques which are to be transmitted, according to the invention the inlet for introducing the operating medium into the operating chamber is arranged at a point of the operating chamber which is situated radially as far outward as possible. The inventor has found the following in particular: in the outlined conditions, where the slip is 100 percent, the operating chamber is not filled to the required amount. Rather, only partial filling is achieved.
The inventor has also found the reasons for this: in the case of the flow-controlled, hydrodynamic couplings which have previously been known, operating medium is supplied to the operating chamber of the coupling over a relatively small radius. If the operating chamber is still empty the supply of operating medium to the operating chamber does not cause any problems. However, as the degree of filling rises, a dynamic pressure builds up in the operating chamber. This acts counter to the pressure of the supplied medium and increasingly hinders the admission of further operating medium, so that complete filling of the operating chamber does not happen at all. However, the further the inlet for the operating medium into the operating chamber is placed radially outward, the greater is the rotational pressure of the inflowing operating medium. This relatively great rotational pressure can overcome the hydrodynamic pressure in the operating chamber. This enables complete filling of the operating chamber to be achieved and therefore transmission of a sufficiently large torque from the driving motor to the machine, for example to the scraper chain conveyor mentioned.
The inlet does not absolutely have to lie on the largest radius, i.e. in the vertex of the operating chamber. However, it should lie in the region of the vertex of the operating chamber.
With the design according to the invention of a flow-controlled, hydrodynamic coupling, a scraper chain conveyor, for example, can be started up from a standstill without any problem even if extremely large amounts of coal have fallen into its collecting region.